EP0659734B1 - Process for the preparation of 3-aminomethyl-3,5,5-trimethylcyclohexylamine - Google Patents

Abstract

The invention is aimed at an improved process for the continuous preparation of 3-aminomethyl-3,5,5-trimethylcyclohexylamine in high yield and high purity (isophoronediamine) from 3-cyano-3,5,5-trimethylcyclohexanone (isophoronenitrile) by aminating hydrogenation with hydrogen and ammonia in the presence of a solid bed catalyst. Isophoronediamine is a raw material for the preparation of isophoronediisocyanate, an amine component for polyamides and a curing component for epoxy resins. According to the invention, the aminating hydrogenation is carried out by allowing a mixture of isophoronenitrile, ammonia and a C1-C3-alcohol to trickle over a trickle-bed reactor provided with a Co and/or Ru solid-bed catalyst at 3 to 8 MPa and a temperature of 40 to 150 DEG C, preferably 90 to 130 DEG C, in the presence of hydrogen and working up the reaction mixture by distillation. A high-boiling by-product fraction, containing a bicyclic amidine, is preferably added to the mixture to be hydrogenated, whereby the yield is appreciably increased.

Description

The invention is directed to an improved process for the preparation of 3-aminomethyl-3,5,5-trimethylcyclohexylamine, hereinafter also called isophoronediamine or IPDA for short, from 3-cyano-3,5,5-trimethylcyclohexanone, hereinafter also called isophoronenitrile or IPN for short called, by aminating hydrogenation with hydrogen and ammonia in the presence of a fixed bed catalyst. The process according to the invention allows the continuous production of isophoronediamine in high yield and high purity.

Isophorone diamine is used as a starting product for the production of isophorone diisocyanate, an isocyanate component for polyurethane systems, as an amine component for polyamides and as a hardener for epoxy resins. Isophoronediamine is usually prepared from isophoronenitrile, the carbonyl group being converted into an amino group and the nitrile group into an aminomethyl group in the presence of ammonia, hydrogen and conventional hydrogenation catalysts. The starting product isophoronenitrile can be obtained in a known manner by adding hydrogen cyanide to isophorone - see DE-OS 39 42 371.

According to the process for the preparation of isophoronediamine from isophoronenitrile described in US Pat. No. 3,352,913, the hydrogenation is carried out in the presence of ammonia and in the presence of known cobalt, nickel, iron or noble metal-containing catalysts at 50 to 150 ° C. and a pressure of at least 50 bar. According to the example, the hydrogenation is carried out in the presence of methanol as the solvent using suspension or fixed bed catalysts. In addition to the desired isophoronediamine, by-products, in particular 3-aminomethyl-3,5,5-trimethylcyclohexanol (isophoronamino alcohol, IPAA), are formed in large quantities. The low yield and a considerable proportion of by-products prove to be disadvantageous in this process.

In an effort to obtain a higher yield of IPDA and to minimize the compulsive occurrence of IPAA, DE-OS 30 11 656 teaches a two-stage process, in the first stage IPN catalyst-free with excess ammonia in 3-cyano-3,5,5 -Trimethyl-iminocyclohexane and this is hydrogenated in the second stage to IPDA. A disadvantage of this process is that, in addition to the actual hydrogenation reactor, a special imine formation reactor is required.

According to EP-B 0 042 119, a further improvement of the process is seen in the isophoronenitrile before the reaction thereof with ammonia and hydrogen in the presence of hydrogenation catalysts at temperatures from 10 to 120 ° C. and pressures from 1 to 300 bar of a pre-reaction with ammonia subject in the presence of inorganic and organic ion exchangers in the ammonium form as imine formation catalysts. While the volume ratio of isophoronenitrile to ammonia should be 1 to 0.5 to 20 in the imine formation stage, this ratio is increased to 1 to 10 to 20 in the hydrogenation stage. The process, which can be carried out in trickle bed reactors, leads to a high yield of IPDA and to a high purity, but the economy of the process is due to the use of two different catalysts and the high excess of ammonia, which is a very high pressure and thus a expensive hydrogenation equipment required, impaired.

EP-B 0 042 119 also discloses a comparative example, in which isophoronenitrile and liquid ammonia are pumped from above into a hydrogenation reactor charged with a commercially available cobalt catalyst. The reaction system is kept at 270 bar with H ₂ ; a certain gas flow is stopped and a certain amount of exhaust gas is discharged. The reaction mixture leaving the reactor below is fed to the working up by distillation. In this embodiment, despite approximately quantitative conversion of the isophoronenitrile, only 48% isophoronediamine and many by-products are obtained. This document does not give any suggestion that instead of a mixture of isophoronenitrile and ammonia, a mixture containing isophorone, ammonia and organic solvent at a substantially low pressure and without the need for an upstream imine formation reaction be passed through a trickle bed reactor.

Another process for the preparation of isophoronediamine is known from EP-A 0 449 089: in two spatially separated reaction spaces, a solution of isophoronenitrile in tetrahydrofuran is first reacted with excess ammonia on acidic metal catalysts and the reaction mixture in a second reaction space with hydrogen in the presence hydrogenated by excess ammonia on cobalt, nickel, ruthenium and / or other noble metal-containing catalysts and optionally basic components at high pressure. According to the example, the mixture leaving the first reaction stage is passed through the hydrogenation reactor from bottom to top; the reactor is operated as a bubble reactor. There are no indications from this document that the reactor can also be used as a trickle bed reactor and that a mixture of isophoronenitrile, ammonia and an organic solvent can be added directly to it.

EP-A 0 394 967 teaches a process for the amination of carbonyl nitriles and iminonitriles and also includes the preparation of isophoronediamine from isophoronenitrile. The starting product is first converted into the aminonitrile under conditions of reductive amination, ie in the presence of hydrogen, ammonia and a hydrogenation catalyst at moderate temperatures; the nitrile group is then converted into an aminomethyl group in the presence of a hydrogenation catalyst which has a hydrogenation action with respect to nitrile groups. The process can be carried out both in reactors using suspension catalysts and in reactors using fixed bed catalysts. Although this process can be carried out at low pressures, it is considered to be a major disadvantage that a strict temperature program has to be followed during the two reaction stages, as a result of which the space-time yield and thus the economy of the process decrease considerably. In addition, the product quality does not meet the requirements, unless special promoters are used, because the 3-cyano-3,5,5-trimethylaminocyclohexane, which cannot be separated by distillation, is usually too high.

A reduction in the pressure in the production of isophoronediamine by aminating catalytic hydrogenation of isophoronenitrile is also possible according to JP-A-4-300852 by hydrogenation with ruthenium in the presence of a supported catalyst. However, this document only concerns suspension hydrogenation conditions, but not those using a fixed bed reactor.

An overview of a technically used process for the production of isophoronediamine from isophoronenitrile is known from SRI International Report No. 1D "Isocyanates" by YU-REN CHIN (July 1983): In the here described process, a mixture of isophoronenitrile, methanol and ammonia with hydrogen is sent over a fixed bed reactor with a supported catalyst - cobalt on kieselguhr. In the described embodiment, the catalyst bed is always flooded (bubble column). The operating pressure is 150 bar. Excess hydrogen is also used, and this excess must be separated from the reaction mixture after the reaction, purified and then recycled after compression. Both the high operating pressure and the technical effort to recycle the hydrogen reduce the economy of this process. As the inventors of the present invention found - see example 3b not according to the invention - this embodiment leads to an increased formation of by-products which are difficult to separate and a reduction in the yield.

The object of the present invention is therefore to improve the disadvantages of the known processes for the preparation of isophoronediamine from isophoronenitrile using a reactor charged with a fixed bed catalyst in such a way that the economy of the process is increased. In particular, the effort for the technical installation should be reduced compared to the previously known methods. In addition, isophoronediamine should be obtained in high yield and isolated from the reaction mixture in a very pure form by means of conventional distillation measures.

We have found a process for the preparation of 3-aminomethyl-3,5,5-trimethylcyclohexylamine (isophoronediamine, IPDA) from 3-cyano-3,5,5-trimethylcyclohexanone (isophoronenitrile, IPN) by using a mixture of isophoronenitrile, an organic solvent from the series of C ₁ to C ₃ alcohols and ammonia at a pressure in the range from 3 to 10 MPa and a temperature in the range from 80 to 150 ° C. in the presence at least one hydrogenation catalyst from the series of cobalt and / or ruthenium fixed bed catalysts is hydrogenated with hydrogen and the reaction mixture is worked up by distillation, which is characterized in that the aminating hydrogenation is carried out in a trickle bed reactor, the mixture of isophoronenitrile, organic solvent and ammonia added to the catalyst bed at the top of the reactor and the reaction mixture obtained after trickling through the catalyst bed is removed at the bottom of the reactor.

The reaction according to the invention is carried out in a conventional trickle bed reactor. The types of such reactors are known to the person skilled in the art: the fixed bed catalyst is arranged in the form of one or more layers in a container; the reactor also has devices for tempering the catalyst layers in order to ensure that the desired temperature is maintained in the respective catalyst layer. Instead of a single trickle bed reactor, several trickle bed reactors can also be connected in series, the reaction mixture emerging from the first reactor being fed in again at the top of the second reactor. The trickle bed reactor or reactors also have suitable devices for adding the reactants, here the mixture containing isophoronenitrile, ammonia and solvent, and the hydrogen, further devices for distributing the liquid on the surface of the first catalyst bed and finally suitable discharge devices for the one leaving the reactor Reaction mixture.

It is an essential characteristic of the process according to the invention that the reaction mixture to be hydrogenated trickles over the catalyst bed and also a sufficiently large gas volume within the catalyst bed exists to allow hydrogen transport through the liquid film to the catalyst surface. It was found that the trickle bed procedure is largely responsible for maintaining a high product yield and, above all, high selectivity. If the reactor is not operated as a trickle bed reactor, but rather as a bubble reactor, that is to say the catalyst bed is always flooded, a substantially lower yield of isophoronediamine is obtained under otherwise identical reaction conditions with regard to temperature, pressure and concentration of the reactants; the bubble mode also leads to a different spectrum of by-products, in particular methyl-isophoronediamine (methyl-3-aminomethyl-3,5,5-trimethylcyclohexyl-amine) being formed. The methyl isophoronediamine mentioned cannot be separated from isophoronediamine by distillation under customary conditions, so that the formation of the by-product mentioned must already be avoided during the preparation of the crude isophoronediamine product. Surprisingly, the by-product mentioned is formed only in a very small amount under the conditions of the process according to the invention. Another disadvantage of the bubble mode is that excess hydrogen must be added in order to obtain H ₂ saturation of the solution, which results in complex recycling of the excess H ₂ .

When carrying out the process according to the invention, hydrogen can be fed to the reactor either in excess or in an amount such that no hydrogen has to be discharged from the reactor and recycled. The supply of hydrogen in excess is less preferred because the technical effort for removing the excess H ₂ , for condensing ammonia and organic solvents contained in the discharged hydrogen and for compressing the purified hydrogen and recycling it is considerable and due to the higher investment caused by this, the cost-effectiveness of the process is reduced; in addition, a lower yield of IPDA was found compared to the driving style without an excess of H ₂ . Hydrogen is therefore preferably not supplied in excess, but only in such an amount that is required to maintain the desired operating pressure.

The aminating hydrogenation is carried out at a pressure in the range from 3 to 10 MPa, preferably at 5 to 8 MPa. Due to the moderate operating pressures mentioned, which are possible when using the sophisticated mixtures of isophoronenitrile, ammonia and solvents and the trickle bed procedure under the demanding temperature conditions, the economy compared to processes that require a high operating pressure is increased by the apparatus requiring a lower investment volume.

The required volume of fixed bed catalyst depends on the LHSV value (liquid hourly space velocity) which is dependent on the operating pressure, the temperature and the catalyst activity and which must be observed in order to achieve a quantitative conversion of isophoronenitrile. The LHSV value is usually at or better than 0.5 h ^-1 . The LHSV value is preferably between 0.8 and 1.5 h ^-1 . An LHSV value in the latter range can be achieved particularly well if the reaction is carried out at a temperature in the range between 90 and 130 ° C. and at a pressure between 5 and 8 MPa.

In addition to the above-mentioned parameters of pressure, temperature and catalyst activity, the LHSV value is also influenced by the selected concentration ratios of isophoronenitrile, ammonia and solvent and the type of solvent used. The mixture applied to the catalyst bed expediently contains 10 to 40% by weight and preferably 10 to 30% by weight of isophoronenitrile and 10 to 40% by weight, preferably 20 to 40% by weight, ammonia. Methanol, ethanol, n-propanol and iso-propanol can be used as solvents. Methanol is preferred as the solvent. Isophoronenitrile, ammonia and the solvent are mixed in such a ratio that a substantially homogeneous solution results. In principle, the aforementioned limit values for ammonia and isophoronenitrile can also be exceeded or fallen short of, provided that a homogeneous solution results. If a mixture containing less than 10% by weight of isophoronenitrile is used, this has a negative effect on the economy of the process.

In addition to the aforementioned constituents, the mixture to be charged onto the catalyst may contain fractions boiling higher or lower than isophoronediamine from the distillative workup of the reaction mixture drawn off from the trickle bed reactor. In addition to residues of isophoronediamine, such fractions can also contain by-products from which isophoronediamine forms again under the reaction conditions. By recycling fractions of this type into the mixture to be used, the yield of isophoronediamine can be increased significantly. It is particularly advantageous if the fraction boiling after the isophoronediamine, which contains 3,3,5-trimethyl-6-imino-7-aza-bicyclo [3.2-1] octane as the main product, apart from residues of isophoronediamine, together with the mixture of isophoronenitrile, ammonia and solvent to the trickle bed reactor. By recycling the fraction containing the aforementioned by-product - a bicyclic compound with an amidine structure - it is possible to significantly increase the yield of isophoronediamine and thus to increase the economics of the process.

The catalysts to be used according to the invention are fixed bed cobalt and / or ruthenium catalysts. These catalysts are usually in the form of pellets, extrusions or other shaped articles. The use of supported catalysts is particularly expedient, with cobalt or ruthenium being on a support with a sufficiently large specific surface area. The specific surface area of the supported catalysts which can be used according to the invention is usually in the range between 5 and 500 m 2 / g (measured according to BET with nitrogen).

The cobalt content of the supported catalysts is generally between 10 and 70% by weight and preferably between 30 and 50% by weight, based on the supported catalyst. The surface of the carrier, which is often an oxidic or silicate material, is partially or essentially completely covered with cobalt, and cobalt oxide may also be present below the surface due to the manufacturing process. Oxides from the series of silicon dioxide, aluminum oxide and titanium dioxide, and also silicates, such as aluminum and calcium silicate, as well as naturally occurring and synthetically produced zeolites and glass frits, are suitable as carrier material. Although commercially available supported catalysts with a high Co content, such as catalysts with 50% by weight Co on aluminum silicate, are described as being essentially completely covered with Co, it was found that catalysts with different supports but with the same specific surface area and the same Co content Selectivity and affect the by-product spectrum. Obviously, the surface of the support of the catalyst is at least partially accessible and intervenes in the catalytic process.

Supported catalysts with ruthenium as the catalytically active component generally contain only a small proportion by weight of ruthenium, usually for reasons of cost between 0.5 and 10% by weight, preferably between 2 and 5% by weight. The preparation of the aforementioned Co and Ru catalysts, which usually comprises an impregnation, drying and forming step, is known to those skilled in the art.

It has been found that when a supported cobalt catalyst isophoronediamine can be obtained in higher yield by the process according to the invention than when using a supported ruthenium catalyst. This is surprising in that the aforementioned documents JP-A 4-300852 and EP-A 0 394 967 described ruthenium catalysts as being particularly effective with respect to the hydrogenation of the nitrile group, which is more difficult to hydrogenate compared to the carbonyl group.

As is known, isophoronediamine occurs in the form of cis and trans isomers - see The Applied Macromolecular Chemistry 153 (1987) 1-13, No. 2502. Examination of the isomer ratio of the isophoronediamine prepared according to the invention showed that the use of a ruthenium catalyst was predominant the cis isomer is formed: cis / trans isomer ratio according to Example 9: 84 to 16. Under otherwise identical conditions, but using a supported cobalt catalyst, the cis and trans isomers are formed in a similar amount: cis / trans Isomer ratio according to Example 8: 60 to 40.

It has also been found that it is possible to produce isophoronediamine with a cis / trans isomer ratio above that obtainable using a supported cobalt catalyst in high yield if the aminating hydrogenation is carried out in a trickle bed reactor in which a Upper layer of a ruthenium supported catalyst and a lower layer of a cobalt fixed bed catalyst is arranged. Ruthenium is a particularly suitable catalyst γ-alumina and a supported cobalt catalyst with an oxidic or silicate support with a cobalt content of 10 to 70 wt .-%, based on the catalyst. Instead of a reactor with two layers of different fixed bed catalysts arranged therein, two reactors can also be connected in series, each of which contains only one fixed bed catalyst; in this case the first reactor contains the ruthenium fixed bed catalyst and the second reactor contains the cobalt fixed bed catalyst. In order to obtain a high yield of isophoronediamine with the desired isomer ratio, it is advantageous if the ruthenium fixed bed catalyst positioned in the first place makes up 3 to 30%, preferably 5 to 20%, of the total catalyst volume.

As has been explained above, the method according to the invention differs in essential points from generic methods of the prior art, which result in significant advantages. By combining the use of a starting mixture of isophoronenitrile, ammonia and an alcoholic solvent and the trickle bed procedure of the reactor equipped with a fixed bed, it is possible to achieve both a high product yield of isophorone diamine and a high selectivity. The formation of undesired by-products, such as methyl isophoronediamine, which has a negative effect on the product quality due to its difficulty in being separated, is largely avoided by carrying out the reaction. The aforementioned combination of features essential to the invention also leads to the fact that the aminating hydrogenation can be carried out at moderate pressures, so that the resulting outlay for the printing apparatus is much lower than in the case of an apparatus for high pressures. Since, contrary to previously known processes using a reactor with a fixed bed catalyst, it is not necessary according to the invention to use excess hydrogen and thus to have to clean and recycle the excess, Elaborate devices for separating, cleaning and recycling the excess H _{2 are} eliminated. Another significant advantage of the process according to the invention is the unexpectedly long service life of the catalysts, which is attributed to the trickle bed procedure: even after several months of operation, neither a reduction in yield nor a change in the by-product spectrum or a change in the isomer ratio was found. Another advantage is that isophoronediamine can be obtained with a certain isomer ratio within certain limits in high yield. In the process according to the invention, there is also no need for a prereaction between the isophoronenitrile and ammonia to form the isophoronimine, which in many documents was regarded as essential for obtaining a high yield and high selectivity in the aminating hydrogenation; In contrast, according to the invention, a solution of the isophoronenitrile in the solvent used is mixed with ammonia immediately before the trickle bed reactor and the mixture is fed to the reactor.

The process according to the invention is further explained on the basis of the following examples without limiting it.

example 1

A reaction tube is filled with 200 ml of hydrogenation catalyst. The feed solution, which contains IPN and methanol, as well as liquid NH ₃ , is pumped into the top of the reactor. The hydrogen also flows into the tube from above. The reaction temperature is kept at 120 ° C. by an oil heater. The pressure is regulated to 60 bar. The liquid is collected in a separation vessel. The gas flow at the reactor inlet is adjusted so that after the separation vessel, a gas flow of 100 Nl / h is set.

A commercially available full Co contact (approx. 50% Co on a silicate carrier) in the form of extrusions with a diameter and length of 4-5 mm was used as the catalyst. The feed solution contained 24% by weight of IPN and 76% by weight of methanol. Of these, 130 ml / h and 70 ml / h NH _{3 were} mixed immediately before the feed to the reactor and the mixture was pumped into the reactor; the LHSV was 1 h ^-1 . After analysis of the product mixture, there was a yield of 88.7% IPDA, based on the IPN used. In addition, 5% were 2-aza-4,6,6-trimethylbicyclo [3,2,1] octane (= bicyclic) and 4.3% 3,3,5-trimethyl-6-imino-7-aza- bicyclo- [3,2,1] octane (= amidine) contained in the product mixture.

Example 2

The experiment was carried out in the same experimental installation as already described in Example 1, with the difference that no gas stream was discharged from the separating vessel, so that only the hydrogen consumed was replenished in order to maintain the reaction pressure of 60 bar. The catalyst, liquid streams and liquid composition were the same as described in Example 1.

Analysis of the product mixture from this test showed an IPDA yield of 89.2%, based on the IPN used. In addition, 4.5% bicyclic and 4.4% amidine were contained in the product mixture. Surprisingly, even a higher yield of IPDA and a reduction of the by-product "bicyclus" are made possible with the procedure without an excess of H ₂ . This experiment was carried out over 2000 h without any loss of yield or changed product range being observed.

Examples 3a and 3b

The same experimental system as in experiment 1 was used. The hydrogenation pressure was 60 bar and the reaction temperature was 120 ° C. The H ₂ flow was adjusted so that 100 Nl / h of H ₂ were discharged from the separation vessel. The feed solution contained 30% by weight of IPN and 70% by weight of methanol. 130 ml / h and an additional 50 ml / h of liquid NH _{3 were} pumped into the reactor. 200 ml of cobalt contact were introduced as a catalyst. Two modes of operation were examined. In the trickle bed mode (3a), gas and liquid flowed through the reactor from top to bottom, in the bubble column mode (3b) the flow through the reactor from bottom to top in the fluidized state.

In the trickle bed procedure (3a), a yield of 87.1% was achieved. After the pure distillation, the product purity was 99.8%; Methyl-IPDA was only detectable in an amount of around 200 ppm.

In the experiment using the bubble column procedure (3b), a yield of 85.5% was achieved. The pure distillation only gave a product purity of 99.5%. The analysis showed that 3000 ppm of methyl IPDA were still present in the pure product. The by-product methyl-IPDA, which has a very negative influence on the IPDA product quality, is practically not separable by distillation.

Examples 4 to 6

The tests were carried out in the same test facility and under the same reaction conditions as described in Example 1. Only the catalyst was varied. The results follow from the table. example catalyst Yield IPDA (%) 4th 5% Ru / γ-Al ₂ O ₃ 82.1 5 Ni 55.3 6 2% Pd / γ-Al ₂ O ₃ 4th

The Ru and Pd were each applied to γ-Al ₂ O ₃ extrusions as a carrier. Examples 5 and 6 illustrate that, compared to the process according to the invention with Ni and Pd catalysts, no satisfactory yields are obtained.

Example 7

8770 g of the reaction solution from Example 2 were freed from the low boilers methanol, NH ₃ , H ₂ O and bicyclic by fractional distillation. A crude solution of 1292 g remained. 1190 g of IPDA were distilled off from this solution at a bottom temperature of 147 ° C. and a pressure of 20 mbar. This corresponds to an insulation yield of 87.3%. 98 g remained in the bottom of the distillation. A further high boiler fraction of 74 g was distilled off from this sump at reduced pressure (10 mbar) and a temperature of 162 ° C. It contained 20% IPDA and 74% amidine. This obtained 74 g fraction corresponds to 5.6% of the amount of IPN used.

In a further experiment, which was carried out analogously to Example 2, the high boiler fraction, 5.6% based on the amount of IPN used, was added. After the hydrogenation and separation of the low boilers and IPDA pure distillation, the isolation yield was 92.3%. By recycling those containing the amidine High boiler fraction was therefore able to achieve an IPDA isolation yield increase of 5%.

By catalytically hydrogenating the fraction containing the bicyclus (boiling point below IPDA) under elevated temperature conditions in a separate hydrogenation reactor, it is possible to increase the yield of IPDA by a further 4%.

Examples 8 to 11

The same experimental system as in experiment 1 was used. The hydrogenation pressure was 60 bar and the reaction temperature was 120 ° C. No H _{2 was} removed from the separation vessel. The feed solution contained 30% by weight of IPN and 70% by weight of methanol. 130 ml / h and an additional 50 ml / h of liquid NH _{3 were} mixed and pumped into the reactor. This test setting was carried out with a ruthenium, a cobalt catalyst and various combinations of the two. The results of this experiment are shown in the table. example Catalyst *) Yield (%) Isomer ratio cis: trans 8th 200 ml co 87.2 60: 40 9 200 ml ru 81.5 84: 16 10th 100 ml Ru + 100 ml Co 83.7 81: 19 11 10 ml Ru + 190 ml Co 86.9 78: 22 *) Ru catalyst: 5% Ru on γ-Al ₂ O ₃ extrudates
Co-catalyst: 50% Co on Al-silicate extrusion

The combination of an Ru catalyst and a co-catalyst, the Ru catalyst being arranged as the upper layer in the reactor, makes it possible to obtain IPDA with a high cis / trans isomer ratio in higher yield than when using an Ru catalyst alone. Catalyst.

Example 12

A reaction tube (diameter 16 mm) of a trickle bed hydrogenation apparatus was filled with 120 ml of commercially available co-supported catalyst (Co on aluminum silicate, 50% by weight Co; BET (N ₂ ) surface area approx. 200 m ² / g). The experiment was carried out analogously to Example 1. The reaction temperature was regulated to 110 ° C., the total pressure (sum of the partial pressures for H ₂ , NH ₃ and methanol) to 60 bar. The feed solution contained 15% by weight of isophoronenitrile, 65% by weight of methanol and 20% by weight of ammonia. 100 ml of this feed solution were added to the trickle bed per hour. After the solution had passed through the trickle bed, the reaction mixture (mol%, based on isophoronenitrile in the feed solution) contained: Isophoronediamine (IPDA) 89.2% Isophorone amino alcohol (IPAA) 2.1% Amidine (see example 1) 4.0% Bicyclus (see example 1) 3.8%

Example 13

Example 12 was repeated with the only difference that another commercially available co-supported catalyst was used - Co on silica, 25% by weight Co, BET (N ₂ ) surface area approx. 200 m ² / g. The reaction mixture contained (data in mol%, based on the isophoronenitrile used): IPDA 87.4% IPAA 1.2% Amidine 4.3% Bicyclus 5.1%

Claims (9)

1. A process for the preparation of 3-aminomethyl-3,5,5-trimethylcyclohexylamine (isophoronediamine, IPDA) from 3-cyano-3,5,5-trimethylcyclohexanone (isophorone nitrile, IPN), wherein a mixture of isophorone nitrile, an organic solvent selected from the C₁- to C₃- alcohols and ammonia, at a pressure in the range from 3 to 10 MPa and at a temperature in the range from 80 to 150°C, is hydrogenated by hydrogen in the presence of at least one hydrogenation catalyst selected from the cobalt and/or ruthenium fixed bed catalysts and the reaction mixture is worked up by distillation, characterised in that the aminating hydrogenation is carried out in a trickle-bed reactor, the mixture of isophorone nitrile, organic solvent and ammonia being introduced at the upper end of the reactor onto the catalyst bed and the reaction mixture obtained after the reactants have trickled through the catalyst bed being withdrawn at the lower end of the reactor.
2. The process for the preparation of isophorone diamine according to claim 1, characterised in that the hydrogenation is carried out at a temperature in the range of from 90 to 130°C and at a pressure of from 5 to 8 MPa.
3. The process according to claim 1 or 2, characterised in that the solvent used is methanol, the mixture introduced onto the catalyst bed contains from 10 to 40 wt.%, preferably 10 to 30 wt.%, of isophorone nitrile and from 10 to 40 wt.%, preferably 20 to 40 wt.%, of ammonia and the mixture forms a homogeneous solution.
4. The process according to one or more of claims 1 to 3, characterised in that the hydrogenation catalyst used is a supported catalyst which consists substantially of an inorganic support, preferably an oxide or silicate material, and cobalt, the catalyst containing in total from 10 to 70 wt.% of cobalt.
5. The process according to one or more of claims 1 to 4, characterised in that a high-boiling fraction which distils off after the isophoronediamine main fraction during the working up of the reaction mixture by distillation and which contains, in addition to residues of isophoronediamine, 3,3,5-trimethyl-6-imino-7-azabicyclo-[3,2,1]octane as main component together with the mixture of isophorone nitrile, solvent and ammonia, is passed to the trickle-bed reactor.
6. The process according to one or more of claims 1 to 5, characterised in that the aminating hydrogenation is carried out in a trickle-bed reactor having an upper layer arranged therein consisting of a ruthenium supported catalyst, preferably ruthenium on γ-aluminium oxide, and a lower layer consisting of a cobalt fixed bed catalyst, the said upper layer and the said lower layer possibly also being arranged, instead of in one reactor, in two separate reactors arranged one behind the another in the sequence referred to.
7. The process according to claim 6, characterised in that the volume of the fixed bed catalyst containing ruthenium constitutes 3 to 30%, preferably 5 to 20%, of the total volume of fixed bed catalyst.
8. The process according to one or more of claims 1 to 7, characterised in that hydrogen is supplied at the upper or lower end of the trickle-bed reactor in a quantity such that no hydrogen is discharged from the reactor and has to be recirculated.
9. The process according to one or more of claims 1 to 8, characterised in that the mixture of isophorone nitrile, solvent and ammonia, which preferably contains from 10 to 30 wt.% of isophorone nitrile and from 20 to 40 wt.% of ammonia and methanol as solvent, is caused to trickle over the catalyst bed of the reactor at an LHSV value (liquid hourly space velocity) of from 0.8 to 1.5 h^-1.